The present invention relates to an information processing apparatus such as a small size information equipment, for example, a notebook computer.
As a display for a notebook computer, a TFT (Thin Film Transistor) type liquid crystal display device (TFT liquid crystal panel) which provides a high display quality but is expensive and an STN (Super Twisted Nematic) type liquid crystal display device (STN liquid crystal panel) which is inexpensive but exhibit high flicker are frequently used. In Japanese Patent Application laid-open No. JP-A-1-277890, an information processing apparatus is constructed by using a dual scan type STN type liquid crystal display device, and in JP-A5-249928, an information processing apparatus is constructed by using the TFT type liquid crystal display device.
FIG. 25 shows a schematic configuration of a conventional personal computer. As shown, a TFT type liquid crystal display device 2 is connected to a personal computer main unit 1 which includes a CPU (central processing unit) 3, a main memory 4, a BIOS (Basic Input/Output System) ROM 5 which stores display specification setting instructions for the TFT type liquid crystal display device 2, a display controller 6, a display memory 7, and a connector device 8 for connecting the personal computer main unit 1 and the TFT type liquid crystal display device 2. The CPU 3, the BIOS ROM 5 and the display controller 6 are arranged on a main board (not shown). The display specification means information on a display system such as a display screen size (the numbers of horizontal and vertical dots), the number of colors and a clock frequency.
FIG. 26 shows a schematic configuration of another prior art personal computer. As shown, an STN type display device 9 is connected to a personal computer main unit 9 which comprises a CPU 3, a main memory 4, a BIOS ROM 10 which stores display specification setting instructions for the STN type liquid crystal display device 9, a display controller 6, a display memory 7 and a connector device 11 for connecting the personal computer main unit 1 and the STN type liquid crystal display device. The CPU 3, the BIOS ROM 10 and the display controller 6 are arranged on a main board (not shown).
In those personal computers, since the display systems of the TFT type liquid crystal display device 2 and the STN type liquid crystal display device 9 are different from each other, the BIOS ROMs 5 and 10 for storing the display specification setting instructions must be provided for each of the display systems. Accordingly, since the main boards for the liquid crystal display device cannot be fully identical, it is not permitted to connect the TFT type liquid crystal display device 2 and the STN type liquid crystal display device to one personal computer main unit 1.
As a result, when a user who has purchased a personal computer which uses the inexpensive STN type liquid crystal display device 9 for economic reasons, desires to change the display device to the high quality TFT type liquid crystal display device 2 because of the flicker problem, he must newly purchase a personal computer which uses the TFT type liquid crystal display device. Further, since a dedicated main board for the liquid crystal device must be prepared for each type of the TFT type liquid crystal display device 2 and the STN type liquid crystal display device 9, it is difficult to promote the sharing of the components used and the manufacturing cost increases. Further, when the personal computers are assembled, the main boards for the two types of liquid crystal display devices must be selected, which takes manpower and time. Recently, application software which handle motion pictures and natural pictures have been becoming popular but since the exchange of only the display device is not permitted, the user must be patient with the STN type liquid crystal display device which exhibits a high flicker and poor image quality or must newly purchase a personal computer which uses the TFT type liquid crystal display device 2. In this case, even if the CPU 3, the main memory 4 and the hard disk do not involve any problems, the user must purchase unnecessary parts.
For an attachment device as shown in FIG. 27 which comprises a bus for exchanging information with the microcomputers 14, and 15 and the personal computer main unit 1 such as a keyboard 12 or a mouse 13, the personal computer main unit 1 can identify the type of the device at the system boot-up, but for the device such as the display device which has no means for conveying information to the personal computer main unit 1, it is not possible to identify the type.